Sport Rocketry—Part 2
Total Page：16
File Type：pdf, Size：1020Kb
RangeRange Safety:Safety: FireFire PreventionPrevention && ResponseResponse We deal in flame in our sport. This angle by cooling the fuel below its ignition by Alan Williams NAR 14137 elemental force is central to what makes temperature or blocking the oxygen, and rocketry possible, but occasionally opens the flame snuffs out. Put a good amount some chance of inadvertent field damage. of water on a fire or cover it over and you Under optimal field conditions, like nice win. green grass and low winds, there is negli- Our possible trouble sources will con- gible risk. But seasonal dry weather, flora, sist of the following: and local climate effects can change the Igniters: Their name says it all. They safety equation. We should never forget can cause problems simply from being spit that fire is eager to blossom from servant to out during misfires and swinging down to destroyer. Here’s what we want to keep in ground level on long firing leads. mind as we have our fun. Exhaust products: Motor heat and sparks can travel. This is obviously true in spades for any high power “effects” propel- First, a little fire lants. Watch carefully at your next night launch and see. science Motor malfunctions: Liberated com- As Zog the Caveman learned long ago, posite and black powder grains from cas- there are three things needed to create fire. ing failures will usually resolve before First, any source of concentrated chemical landing, but not always. energy to serve as fuel (dry wood, grass, fo- Ejection charges: Any model landing liage, mulch, etc.). Second, oxygen to com- before ejection can also cause problems bine with that fuel. Third, a heat source and must be carefully observed. sufficient to make fuel and oxygen interact. And of course, other casual social ac- These elements are called the “fire triangle” tivities such as cooking, smoking, or fire because without all three participants, eating might happen in tent areas. combustion cannot occur. What keeps it going is the rapid liberation of hot com- bustible gasses as the fuel swiftly oxidizes. Prevention steps (This creates the inconvenient fourth side Again, normally we are probably the of the triangle, but let’s overlook that!) And safest thing happening on a given field. the reaction speed is key: the only differ- That’s because we take all prudent precau- ence between those rust spots growing on tions. If state or local authorities declare a your car and a burning sparkler is the oxi- “Red Flag” fire danger day in your region, dization rate. I’ve seen breathtaking NASA cancel the launch. There is no excuse to video of stainless steel pipes literally blaz- do otherwise. If conditions are less acute, The NAR range crew responds quickly to a burning rocket ing like fireworks when exposed to high you proceed at appropriate levels of cau- at NSL 2016. pressure pure oxygen flow. Break the tri- tion. Only the most rigorous preparation SPORT ROCKETRY JANUARY/FEBRUARY 2018 29 and inspection procedures should be ap- plied to each model to be flown. The other extensions of procedures are: Launch area prep: Any dried grass, thatch, leaves, or other fuel should be raked well away from the launch zone; the result- ing refuse needs to be moved well upwind and/or disposed of. I once saw a dry grass pile ignite more than twenty feet from an A-impulse contest flight. If you have water to spare, you may want to spray down the area under the launchers at intervals. Also, inspect the ground near the launchers as the day goes on. Foot traffic will probably degrade the ground cover there. Launchers: Try to get them elevated off ground level and insulated from burn- able items (with welding blankets, tarps, wet ground cloths, or pavers). Blast deflec- tors should be angled or designed to throw exhaust products back up so they can cool in mid-air, rather than being channeled down toward the ground. Exhaust flame impingement damage on the rocket can be controlled by supporting the model a An Indian Pump five-gallon water fire extinguisher with flexible backpack and hand-pump nozzle. This extinguisher was purchased for $135 by the Zia Spacemodelers Section using NAR safety grant money. bit higher up the rail. A very good idea is the addi- tion of an upward-directing lip at the deflector’s edg- es, either by bending the deflector or adding some nonflammable material like plaster of Paris or tile grout to form a ramp structure. Large clay flowerpot saucers are relatively cheap and work well, though they’re a bit fragile (the edge lip is built right in the design). In any case, modelers should carefully cen- ter the motors above the deflector, which should be realistically sized for the model at hand. Suggested fire response supplies While some of this should be standard equip- ment for every launch, prevailing conditions may warrant extra safety measures. You should always bring some combination of the following. Fire flap- pers or shovels. Sand buckets to bury small prob- lems close-in. Metal (not plastic) bow rakes to re- move that dry plant material. And a place to put it! And always have some form of extinguisher backed up with a large surplus of water. Fire extinguishers: Ideally, you want something like the “Indian Pump” backpack system. This is a classic hand–pumped water spray tool used to fight A fire flapper and a brush fires. If approached properly, your local fire refillable pressurized water service may well loan you one or two. Commer- fire extinguisher. cial “Class A” water units are available that can be Photo by Ed Pearson. refilled, then recharged with any air compressor. I also used a pair of three gallon pressurized metal 30 JANUARY/FEBRUARY 2018 SPORT ROCKETRY garden sprayers to good effect for years. To use the other tools: In blowing winds, established grass and I simply bored out the nozzle tips to al- Fire flappers are floppy sheets of rub- brush fires can surge forward faster than low more water flow and pumped them ber mounted on poles. They work by beat- you can run. Make sure everyone main- to high pressures. They had the advantage ing down the flame plume and denying the tains situational awareness. Have spe- of being lighter weight so we could get to combustion point fresh air. You might find cific people assigned fire watch, suppres- a smoldering spot fast. However, today’s it more effective to drag the flapper along sion, and fire service reporting duties. The garden sprayer systems commonly have the ground to smother the fire, rather than Range Safety Officer will have command. plastic wands and nozzles that might melt slapping away at the flames. A flat shovel- If flames show the slightest sign of get- near flames. Look for metal alternatives. head can have much the same effect. Care ting away, call your fire service now! They My sprayers were dedicated to fire sup- must be used to prevent burning materials would much rather roll up on a fire that’s pression; you don’t want pesticide or other from being blown forth to cause new hot been killed than fight a large event because residues creating unknown hazards. spots. of a reluctance to call for help until it broke Remember that many extinguisher In arid regions, dirt or sand poured, free. types assume indoor use against specific raked, or shoveled onto a small fire like- The preceding should not be taken as fire sources. You are fighting a “Class A” wise denies oxygen and snuffs the fire. saying that we are turning the nation to a (wood, paper, organic cloth materials) fire. Metal rakes can also be used to break up wasteland of carbonized burn scars. In fact Because of wind effects inert vapor extin- flame sources to make water more effec- we have a good record of stewardship on guishers using CO2, Halon, or Carbon-Tet- tive. The NAR Section Safety Grant pro- our fields. This is because we always try rachloride will have little effect on grass or gram can make this equipment easy to pro- to anticipate and control problems. But, in brush fires. Soda-acid units (which com- cure, at little or no cost to your club. the rare event that things go wrong, you bine vinegar and baking soda to produce If stepping in hot areas, remember that want to have a plan and the equipment to a CO2-liquid mixture) will have no advan- plastic athletic shoe soles can melt or catch respond fast and right. tage over water outdoors. Dry chemical fire themselves. (Thanks to Pr. Georges Co. Maryland systems will work on grass fires, but their Grass fires should be fought only from Station 39 Chief Pete Mellets and Instruc- effectiveness in this application is not high. the rear (up wind) or sides. An attack from tor Tom Cusack for useful information They smother the flame with a combus- down wind by untrained persons without tweaks.) tion-interfering powder that must land in protective gear must never be attempted. the right spot to work. They must also be serviced or replaced after even the small- est discharge because the powder-fouled Are You Ready to Make the Jump? valves let pressure leak out afterwards. So, 18 chapters, 388 pages, 800 photographs and water is your best weapon. But use any- thing at hand. Even a two-liter soda bottle almost everything you need to move ahead in shaken and vented at a fire is better than High Power Rocketry, Level 1 through Level 3.